surging when heater on
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Joined: Oct 2006
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surging when heater on
Hey guys, I have a strange surge or lope when my in cab heater is on. I noticed it the other day waiting to pick up the wife in a parking lot if I bring the idle up to 1000 or so rpms and switch the heater on (ac or heat dont matter fan speed dont matter) it makes a clunk under the hood and my rpms drop to about 550 for 10 seconds then runs back up to 1000. This will continue every half minute. If it idles at normal speed iI only here the clunk. Any ideas? Its a 2003 6.0 79000 miles EGR unpluged and no engine light.
Junior User
Joined: Nov 2007
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A/C Clutch engaging?
The only reason I suggest this is that I recently learned that in addition to my previous understanding re. A/C engagement in the Defrost position (in addition to those positions marked w/ "A/C"), this also occurs in other HVAC control positions as well (e.g. "Face+Foot": this surprisingly uses the Air Conditioning). Vent (Face only, 1 click to the left of OFF) and OFF are the only two positions where the A/C is disabled. It will cycle in all other positions provided that the ambient air temperature is above approximately 43 degreess F.
I did not have the idle drop that you have (down to 500), but I did hear the repetitive, cyclical "clunck" whilst using "Face+Foot", and was puzzled by it. Then one day I saw condensate dripping and I was wondering why my A/C was cycling.
Answer: it's supposed to. Whoduv thunk?
Mark
I did not have the idle drop that you have (down to 500), but I did hear the repetitive, cyclical "clunck" whilst using "Face+Foot", and was puzzled by it. Then one day I saw condensate dripping and I was wondering why my A/C was cycling.
Answer: it's supposed to. Whoduv thunk?
Mark
Senior User
Joined: Apr 2007
Posts: 368
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From: Kansas
I had the same problem with my 04. It really drove me crazy. Some times it would do it so bad it would make my ears pop. They change the heater box, controls and every thing that goes with it to no avail. What is happening so I was told, when you turn the heater / air on, the ac pump kicks in. When it dose that the condenser under the hood jumps and makes the clunking noise. They ended up zip tying the condenser to the frame and it didnt do it as bad. Just a thought since mine was in the shop about 15 times for the same thing.
Senior User
Joined: Apr 2007
Posts: 368
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From: Kansas
After all the trips in for this and numerous other things I finally cured the problem. I bought an 07 and have been very pleased so far. I only have 8k on my new truck so far and no problems. At least the dealership where I bought the truck took care of me when I traded it in. Blue book was 28k and they gave me 40k because of all the problems that I had with it. But we all know it was because the had rebates from hell on the 07's trying to make room for the 08's. Either way I am finally happy with my truck.
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